11 STEAM GENERATORS; DRYING AND VENTILATING APPARATUS, NAMELY, VENTILATING FANS FOR INDUSTRIAL USE, AND DRYERS FOR INDUSTRIAL USE; AIR CLEANING APPARATUS, NAMELY, AIR CLEANERS, PURIFIERS, AND AIR DRYERS; WASTE WATER PURIFICATION UNITS; AND DEDUSTING APPARATUS, NAMELY, DUST ELIMINATORS AND DUST ARRESTERS